Recent data indicate dramatic increases in both awareness and use of electronic cigarettes (e-cigarettes) in the USA. Moreover, e-cigarette use is higher among current smokers than former- or never-smokers. This is of considerable public health significance since very little is known about the effects that e-cigarettes have on brain functioning, behavior, and physiology. This P30 application includes two key projects: project 1 will consist of two laboratory-based experiments and project 2 will be a community-based experiment. For the laboratory-based experiments, non-treatment seeking cigarette smokers (N=90/group) will be evaluated after exposure to e-cigarettes (0 or 18 mg) or their own cigarette on three separate visits: This will allow us to directly compare and evaluate e-cigarettes against smokers' preferred brand of cigarettes. In the first experiment (Project 1a), behavioral and physiological responses to smoking cues will be evaluated using virtual reality cues. In addition, this experiment will assess changes in smoking severity via a dual-component self-administration session in conjunction with the CReSS device to assess smoking topography. In the second experiment (Project 1 b), functional magnetic resonance imaging will be used to measure brain responses to general reward, and to pictures of cigarettes and e-cigarettes. In addition, pictures displaying the Surgeon General's messages about cigarette smoking will be shown to evaluate perceptions about adverse health consequences of cigarettes and e-cigarettes. Upon completion of either laboratory-based experiment, all participants will proceed into the community-based study, project 2, in which all individuals (N=180) will be presented with e-cigarettes (18 mg). In this study, participants will visit the clinic once weekly for 4 week as well as 1 month follow-up. Daily assessments will be conducted using ecological momentary assessment (EMA). EMA assessments will include initiation and continuation of e-cigarette use, assessments of changes in use of own cigarettes, and assessments of perceptions, satisfaction and acceptability of e-cigarettes. Additionally, we will evaluate continuation of e-cigarette use a 1-month follow-up.